runmdn
Overview
runmdn is a command that enables a Unix client with the bind4 or bind8 based resolver libraries to support multilingual domain names without recompiling. Specifically, the name-resolving API (for example, gethostbyname) accepts host names denoted in the local encoding (EUC-JP, etc.) of the application, and also returns multilingual host names in local encoding.
Using runmdn to enable clients to support multilingual domain names is the easiest and least time-consuming of the methods provided by the mDNkit. However, it cannot be used with some systems and does not work with certain commands. See the Section Limitations for details.
Setup
To use runmdn, the encoding and normalization schemes must be specified in the shared mDNkit client file. Refer to mDNkit Resolver Configuration for information on how to configure this file.
runmdn automatically senses the local encoding used by an application, but this may sometimes fail. In such an event, refer to Local Encoding for procedures to deal with the situation.
Usage
runmdn is very easy to use. All that has to be done is to append runmdn, the command name, to the beginning of the application startup command.
% runmdn command [argument...]
For example, to use the telnet command to connect to the host "私の会社.jp", do as follows.
% runmdn telnet 私の会社.jp
Limitations
runmdn is the easiest method for enabling clients to support multilingual domain names of all the methods that the mDNkit provides. However, this method may not be applicable for some clients.
runmdn uses the dynamic link (a library pre-load function) of system-owned shared libraries to replace some of the functions of the resolver libraries linked to an application with versions with functions that can handle multilingual domain names to enable handling of multilingual domain names. The functions that are replaced are functions used in bind4- and bind8-based resolvers.
As a result, runmdn operation has the following limitations:
- As shared library links are used, the system must be able to use shared libraries.
- The system must have a preload function that operates with the use of LD_PRELOAD, an environment variable, or similar mechanism.
- runmdn can only be used for commands that link resolver libraries statically.
- If the system library does not provide the iconv() function, an external library that does can be used, but it must be a shared library.
- System resolver libraries must be based on bind4 or bind8.
- As setuid commands cannot use the preload function for security reasons, do not use such commands.
When these limitations make use of runmdn impossible, other methods provided by the mDNkit (for example, dnsproxy or bind9 patches) can be used.
